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Investigation of strengthening mechanism of commercially pure titanium joints fabricated by autogenously laser beam welding and laser-MIG hybrid welding processes
摘要： In this study, in order to achieve a better understanding of the strengthening mechanism in the commercially pure (CP) Ti welds, autogenously laser beam and laser-MIG hybrid welding of 4.2 mm thick CP-Ti plates were performed and the correlation between microstructure, texture distribution and the mechanical properties were systematically investigated. Microstructural coarsening and increase in microhardness were observed in the HAZ and WZ. The tensile test results suggested the base metal was the weak point of the joint for both welding conditions. The EBSD observations confirmed that a large number of 1012 and 1122 twin grains occurred in the HAZ and WZ of both welded joints, while a higher concentration of these twin grains were found in the laser-MIG hybrid joints. High concentration of the twin grain boundaries can act as barrier to stop dislocation slip during deformation and therefore contribute to the strengthening of the welds. The existence of very small twin grains and acicular α phase in HAZ and WZ would equivalently reduce the averaged grain size and therefore induce an increase in strength based on Hall-Petch’s law. In addition, the averaged Schmid factor of BM is higher than that of the WZ and HAZ in both welding joints suggesting that the grain boundary sliding will take place preferably in BM during deformation so that the necking and fracture occurred in base metal during tensile tests of both welding joint specimens.
关键词： Texture,Mechanical property,Laser-MIG hybrid welding,Strengthening mechanism,Commercially pure titanium,Laser beam welding,Microstructure
更新于2025-11-28 14:24:20
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Microstructure and Properties of Graphene Oxide-doped TiO2 Coating on Titanium by Micro Arc Oxidation
摘要： Micro arc oxidation (MAO) coatings doped with graphene oxide (GO) were prepared on pure titanium by adding GO and sodium dodecyl benzene sulfonate (SDBS) into a sodium silicate solution. The as-deposited coatings were comparatively analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The binding forces of the MAO, MAO+GO and MAO+GO+SDBS three coatings were measured by a scratch tester. The mechanical property of the three coatings was analyzed using the nano-indentation technique. The corrosion resistance of the coatings was tested by the electrochemical system in 3.5% NaCl solution. The photocatalytic activity of the prepared samples was evaluated by determining the degradation of methylene blue (MB) solution. The results showed that compared to the MAO coating, the morphologies and phase compositions of MAO+GO and MAO+GO+SDBS composite coatings were significantly different. These two composite coatings all had superior photocatalytic activity. Especially, the MAO+GO composite coating still had enhanced binding force and excellent corrosion resistance. Furthermore, the relationship between the microstructure and the properties of these three MAO coatings was analyzed.
关键词： pure titanium,graphene oxide,micro arc oxidation,properties,microstructure
更新于2025-09-23 15:23:52
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Analysis of back-weld spatters in laser welding of CP-Ti
摘要： The laser welding of commercial grades of pure titanium plate TA2 with 0.5 mm was taken, and the back area of the molten pool was photographed by high-speed camera. Also, the reasons of back spatters were studied. Spatters on the back side of the plate have three main types: continuous spatters, periodic spatters and no spatters. All continuous back spatters are accompanied by the appearance of keyhole, and the keyhole can be observed at the moment when periodic spatters appear. The downward shear stress applied by the downward jet of metal vapor from the keyhole is an important reason for backside spatter. Increased laser power or welding speed will increase shear force, eventually contributing to more spatters. When the defocused distance is increased to 30 mm, the keyhole is completely obscured on the back side, so there is no spatter at this time.
关键词： Backside spatter,Laser welding,Keyhole behavior,Commercial pure titanium
更新于2025-09-23 15:19:57
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Non-isothermal <i>?2</i> grain growth behaviour of pure titanium under laser quenching
摘要： The primary understanding of laser-induced non-isothermal prior β grain growth behaviour of titanium alloys is given by adopting laser quenching on pure titanium. Results indicate that the prior β grains grow obviously within the limited laser interaction time. By establishing a finite element model combined with numerical approximations, the growth activation energy of prior β grain under laser-induced non-isothermal condition is determined as 44.4 kJ/mol, which is comparable to that under isothermal conditions. Grain boundary migration behaviour of pure titanium under laser-induced non-isothermal conditions is the same as that under isothermal conditions, but the prior β grain growth kinetics is largely accelerated due to the high heat input from the laser beam.
关键词： non-isothermal,Laser processing,pure titanium,crystal growth
更新于2025-09-23 15:19:57
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Structure and Phase Composition of a Ti Film–Al Substrate System Irradiated with an Intense Pulsed Electron Beam
摘要： Commercially pure A7 aluminum was exposed to surface modification in a single vacuum cycle which included vacuum arc evaporation and deposition of commercially pure titanium and intense electron beam irradiation and melting of the film–substrate system using a plasma-cathode pulsed electron source. The deposited Ti film thickness was 0.5 and 1 μm. The irradiated Ti–Al system revealed a multilayer multiphase structure consisting of submicro- and nanosized elements with intermetallic inclusions Al3Ti, Al2Ti, and TiAl3. The Ti film during irradiation broke up into fragments with their immersion in the molten Al surface layer to a depth of 20 μm. The modified material surpassed the initial aluminum in wear resistance by a factor of 2.4 and in microhardness by a factor larger than 4. The main cause for the high surface hardness and high wear resistance of the modified aluminum was likely the formation of both the intermetallic particles and the Ti-hardened transition layer.
关键词： low-energy high-current electron beams,commercially pure aluminum,commercially pure titanium,film–substrate system,properties,structure
更新于2025-09-19 17:15:36